Fine and coarse control



W. H. NEWELL FINE AND COARSE CONTRL Y July 30, 1957 Filed May 4, 1954 2 Sheeps-Sheet l COA/955 ATTORNEY United tatesA FINE AND COARSE CONTROL William H. Newell, Mount Vernon, N. Y., assigner to The Sperry Corporation-Ford Instrument Company Division, Long Island City, N. Y., a corporation of Delaware t Application May 4, 1954, seria1N0.4z7,44i

6 claims. (ci. sli-s2) This invention relates to means for causing a driven member to follow or, reproduce the movement of an initiating or signal member, andfmore especially to means for bringing such a follower, into synchronizing agreement with a moving, signal member.

Among the .principal objects which the invention seeks Vto accomplish is the shortening of the time for bringing the `follower into synchronization with the signal and the avoidance of overrun andthe effecting of smoother synchronization than has heretofore been attainable.

Another important object of the invention is simplicity and high degree of accuracy in performance and in the measurement of quantities employed in the control.

While the invention has general'utility in the reproduc- /tion of motion', it has been especially designed for use in gun fire control in the` synchronizing of guns with a "signal produced by'a sighting device in training upon and following a target. This invention contemplates the incorporation and use in the synchronizing control of a factor termed herein and known to those working in the s artras error reducer, that is, a quantity proportional to the v signal rate.

maining angle, resulting usually in overshoots because of the peculiar system constants needed for reducing dynamic ferrors.

In the copending application of William H. Newell,

iSerialNo. 5577,982, filledOctober l0, 1944, now Patent No. 2,763,988, issued September 25, 19,56, there is disclosed `the introduction of a control responsive to the signail krante inthe case of a moving signalinaddition to the Vcontrol responsive to the positional disagreement or error. This was for the purposevof eliminating the lag inherent in the error responsive control and is embodied in a hydraulic mechanism in which through a pilotfpiston the error fed frorna comparisonfdiflerential operates to dis- `place aquantity of hydraulic iluid proportional to the error and thus cause acorresponding tilt of the control member of a variable speed hydraulic gear. In accordancey withthe invention of said application there is a sup- Vvplmental control responsive to the signal speed which effects a displacement of an additional volume of hydraujllic fiuid;'proportional to thesignal lof speed. The function of this =so-called error reducer is to generate an expressionof signal velocitywhich is vapplied to tilt the speedgear so that the resultant error which will be operated on by the main servo will be at a minimum.

Y VIt wasV foundthat with the introduction of the error reducer it became possible in connection with fine and Acoarse control systems to modify the system constants so that the overshoots weregreatly reduced. The Newell PatentNo. 2,405,046 describes means for obtaining synchronizing rates proportional to errors control from coarse to fine.

The present invention contemplates the obtaining of such proportionality in a fine and coarsel control system but without the use of the special equipment described in that patent. Furthermore this invention contemplates the employment of the error reducer in connection with such a system. i

In accordance with the invention the hydraulic synchronizing device of said application Serial No. 557,982 is replaced with an electrical synchronizing system. This system is operated by control transformers and allows synchronizing at maximum velocities until a predetermined error position is reached, after which the rate of synchronizing is proportional to the remaining positional error. This type of control achieves a decrease in the synchronizing times and produces a smooth decelerated approach to the synchronized position without the. undesirable roughness and Aoverrunning previously encountered.

The, invention will now be described in connection with the accompanying drawings after which the invention will be pointed out in claims.

Fig. 1 is a block diagram of a system embodying the invention; v v v Fig. 2 is a graph showing a characteristic synchronizing curve when synchronizing to a Vfixed signal; and

Fig. 3 is a graph showing a characteristic synchronizing curve when synchronizing to a 10 per second Vincreasing signal. l

For the purpose of illustration the invention will be described as applied to the synchronizing of a gun mount to a gun order signal. y

The illustrated system utilizes electromechanical cornponents in the control in lieu of the hydraulic components of said application, andr specifically it uses control transformers to receive the automatic gun order signals which, as is well'known, act'as differentials. The gun order signal is compared with the gun mount response in the control transformers and the output voltage therefore represents the error and is transmitted-to the tilt servo the output of which is proportional to the voltage received. The tilt servo operatesto tilt the stroke rod of the hydranlic speed gear.

The illustrated system hasacoarse vcontrol transformer 10 and a fine control transformerv20. The mechanical response 1l. of the hydraulic `speed gear 12 is fed back to control transformers 10 and 20. The comparison or error output of control transformer 10 is transmitted to amplifier i4 and the error output of control transformer 20 is transmitted to amplifier 15 which is a summing or combining amplifier and to error integrator 16 the output of whichv is also transmitted to amplifier 15. -This amplifier thus receives and combines the signalof error and the integral of error.

The coarse error signal output 17 from amplifier 14 and the modified fine error signal output 18k from amplifier 15 are transmitted to thecontrol switching unit 19. This is a voltage sensitive relay and a control switching signal 2i is obtained from the coarse error amplifier 14 and the signal is used in the control switching unit 19 to determine whether the coarse error or fine error will be in control of the speed gear 12. l

From the control switching unitv the error voltage is transmitted to asumming amplifier 22` which also receives the voltage output of a rate generator of an error and for switching reducer, as will later appear. The output of amplifier 22 is transmitted to the' tilt servo 23, the output of which, as above stated is proportional to thelvoltage received by it. This tilt servo controls the setting of the tilting box or stroke rod ofthe hydraulic gear and thus determines the direction and speed of'response.

`The control switching unit 19 will disconnect the fine error signal from "the `tilt servo and also connect the coarse error signal to the tilt servo when the gun error reaches .a ,predetermined value,"generally selected as approximately'Zf/i' o'f arc, resulting'in'.acontrolswitching signal voltage large enough to require this switchingof control.

The error reducer referred to is diagrammatically represented 1in .the'box so entitled inFig. l. It comprises a :control .transformer 24 which alsoreceives the automatic gun order signal. `Its output is'transmitted to Iarnpliler 25 and the amplified -voltage from this amplifier is .transmittedtoa servomotor '26. `The mechanical output-.of the .servomotorlo isfedlbaok .to control transformer.24, the connections of the control 'transformer vbeing vsuch that .'its .output voltage :is proportional to vthe .signal velocity or rate. 'The servomotor 26 therefore `is .driven at a ,rate proportional to .the vsignal rate .and fit 'is :connected to dive an -electric generator '28 Vwhich is .termed `a rate generator since llits voltage output .29 lis -proportional lto the gun .orderisignal velocity.

This error reducer signal voltage 29 'is transmitted to the summing amplilier"22, as diagrammatically indicated in Fig. 1 and combines .withV the error voltage Lb'eing 'transmitted .fromthe control switching unit 19 .to determine vthe voltage controlling .the rtilt servo 23 and therefore the response speed ofthe speed gear,

As represented 'in `Fig.'2 the coarse error voltage will be ofa magnitude to tilt the servo at full stroke when the gun `errorreaches some selected value, shown as 20 of arc. That value is of course .arbitrary and will be modifed'to suit conditions. "The .response speed curves of vFigs.'2 and 3 indicate that the maximum response speed at full stroke is 25 .persecond although ofcourse "this iis arbitrary and will depend vupon the constants of v'the system. l

Fromrthe above it is apparent that'the 4combining of the error reducer voltage with .the .error voltage from Vthe "coarse control transformer with .a moving signal will 'advance orretard 'the` point or degree of .error at `which Athe response changes from .maximum -speed to a vcontrolledspeedproportional to the amount yof error. Whether the error reducer voltage advances or retards 'this point dependslupon whether thesignalis an increas- "fing lor "decreasing signal.

'fBy wayofexample,'let it-'be .assumedthat thereceived gun 'order Vsignal calls vfor the gun yto .be.synchronized to a fixed signal .and that there .isa present-error of 45. "fhe Vgun jordersignalindicating the .error of 45 .is.re -ceived'by the coarse control transformer 10 .and .the V"control switching tunit '.119 places the .coarse .channel in controlofthe 'tilt.servo. ".Ihesignalis yalsoreceived by the-'error :reducer 'control .transformer I.24 but .since the 'signal speed is' zerolthe.. servomotor response v.2.7 immediately'positionsthe control-transformer tozero voutput and r` thereis therefore no rate voltage generated.

The result'ist'he conditionillustrated in Fig. 2. The 'coarse"errorvoltage"17 vis of a magnitude to position the tilt servo to full .speed which is maintained until the selected'pointfnamelvan error of.20 is reached, when deceleration lbegins'an'd the..response is asymptotic, the `output of'thet'ilt servo becoming proportional to the received voltage which `isfpropor'tional :to the error. At 2%" of-error'the control -switchesfrom vthe coarse to the fine "channel and synhroriism .is f achieved `smoothly andwith^no 'appreciable overshooting. .In Fig. ,2 the portion of the curve representing .the condition of vfull speed `is marked A ancl the .portion representing deceleration into .synchronismf is ..marked..B.

Fig v3..repr'esents the curve when .synchronizing toa signal ."increasing at `the .rate :of -.-10 per second. In "this fthe .error..reducer voltage .or signal is proportional to..the..signal rate vandis .addedto the ycoarse? signal error "voltage Lin the .summing .amplifier ..22 .and :modifies the .response so\astollowlheffull.speednfsZS per second to continue until the gun is nearer the signal. In the illustrated example this point where deceleration begins and from which the error decay is at a rate proportional to the error is at 121/2 At synchronism the gun moves with the signal at 10 per second and since there is no error voltage the response is wholly from the error reducer voltage.

With a decreasing .signal lthe-error ,reducer voltage will have the opposite elect causing the deceleration to start .at a point of larger error than would be the case without the error reducer. For example, with a signal decreasing at the rate of 10 per second, the point of change would be 271/2 of error. In other words, with agiven maximum gun mountspeed, the deceleration has to start farther from synchronizing position, when the signal is approaching the mount train angle than is the case when the signal is moving in the same direction as the mount.

It is apparent therefore that the described combination ofthe error reducerwith the basic fine and coarse control permits the error reducer effect to be applied during synchronizing, resulting in smooth synchronization. Also the error reducer allows of longer operation under maximum 'speed and shortensthe time required for syn chronizing. p

vIt is obvious that the invention is independent of the particular electromechanical components employed and that the illustrated system may be modified in various respectswithout departing vfrom the scope of the invention as defined inthe following claims.

What is claimed :is:

l. Motion reproducing mechanism comprising a variable vspeed power device for driving a follower member, an electrical servoin .control of the power device, the output of the `servo being proportional to the voltage received, a control transformer connected to receive electrical signals `representing motion to be reproduced by the follower member, means for .delivering to the control transformer the response of the power device, means for delivering the output voltage of the control transformer to 4the servo, means for generating a voltage proportional to the velocity of said `electrical signals and means for addingsaid'voltage tothe output voltage of the control transformer.

'2. Motion reproducing mechanism as claimed in claim vl inwhich the means for generating a voltage propor- .tional to the velocity of said electrical signals comprises a second control transformer connected to receive said signals, a servomotor connected to receive the output of said. second control transformer, means to deliver to the said .second .control transformer the mechanical output of said servomotor, andanelectrical generator driven by said servomotor. f

3. .Motion reproducngmechanism as claimed in claim 2 in which thereis a summing amplifier connected to said electrical servo and the `voltage outputs .of said rst mentionedlcontrol transformer and of said generator are combined in said summing amplifier.

4. Motion reproducing mechanism comprising a variable .speed hydraulic gearvof the type having a tiltable member for controlling the direction and speed of the output of the gear, an Aelectrical servo in control of the tiltable member, the .output of the servo being proportional .to the voltage received, a control transformer connected to .receive electrical .signals representing motion to be reproduced-by .the .output of the hydraulic gear, means .'fordelivering. to the control transformer the said output of the hydraulic gear, -means for amplifying the outputof the .control transformer, a second control trans former connected to receive said signals, an amplifier for the output of the second control transformer, a servomotor connected tothe output of said last mentioned ampliferymeans for delivering to the second control .transformer theroutput of thesaid servomotor, an elec ..tricalgenerator:driven bythe .saidfservomoton ;a voltage summing member connected to the said electrical servo, and means to feed into the voltage summing member the amplified voltage output of the rst mentioned control transformer and of the said electric generator.

5. Motion reproducing mechanism comprising a variable speed hydraulic gear of the type having a tiltable member for controlling the direction and speed of the output of the gear, an electrical servo in control of the tiltable member, the output of the servo being proportional to the voltage received, a coarse signal channel and a line signal channel, each including a control transformer connected to receive electrical signals representing motion to be reproduced by the output of the hydraulic gear, means for delivering to both control transformers the output of the hydraulic gear, an amplifier connected to the output of each control transformer, a voltage summing member connected to the said electrical servo, a control switching device for :selectively connecting the outputs of the coarse and line circuit ampliers to the voltage summing member, the said control switching device being responsive to the voltage output of the coarse circuit amplier, means for generating a voltage proportional to the velocity of the said electrical signal, and means for conducting the said velocity proportional Voltage to the said summing member.

6. Motion reproducing mechanism as claimed in claim 5 in which the means for generating a voltage proportional to the velocity of said electrical signals comprises a third control transformer connected to receive said signals, a servomotor connected to receive the output of said third control transformer, means to deliver to said third control transformer the output of said servomotor, and an electrical generator driven by said servomotor.

References Cited in the file of this patent UNITED STATES PATENTS 2,630,282 Halpert Mar. 3, 1953 2,648,041 Perkins Aug. 4, 1953 2,670,454 Wilson Feb. 23, 1954 2,698,407 Pease Dec. 28, 1954 

